The command line interface is a throw back to before the Windows GUI was invented and everyone used MS-DOS (late seventies early eighties). You may input MS-DOS commands at the command line...
The Command Driven Interface, sometimes also referred to as a "CLI" or "Command Line Interface" is operated via the keyboard alone. It can display ASCII text characters and accept them as valid...
There are a couple different "terminal" programs, you can either find them in your desktop managers "start" menu or you can press Alt+F2 to bring up the run menu and in KDE enter "konsole" and gnome...